Through a cooperative effort between Hsin-Yi Wang and Dmitry
Baryshkov, we have realized the dev_err_ratelimited() in the
mipi_dsi_*_write_seq() macros was causing quite a bit of bloat to the
kernel. Let's hoist this call into drm_mipi_dsi.c by adding a "chatty"
version of the functions that includes the print. While doing this,
add a bit more comments to these macros making it clear that they
print errors and also that they return out of _the caller's_ function.
Without any changes to clients this gives a dramatic savings. Building
with my build system shows one example:
$ scripts/bloat-o-meter \
.../before/panel-novatek-nt36672e.ko \
.../after/panel-novatek-nt36672e.ko
add/remove: 0/1 grow/shrink: 0/1 up/down: 0/-21496 (-21496)
Function old new delta
nt36672e_1080x2408_60hz_init._rs 10320 - -10320
nt36672e_1080x2408_60hz_init 17412 6236 -11176
Total: Before=32147, After=10651, chg -66.87%
Note that given the change in location of the print it's harder to
include the "cmd" in the printout for mipi_dsi_dcs_write_seq() since,
theoretically, someone could call the new chatty function with a
zero-size array and it would be illegal to dereference data[0].
There's a printk format to print the whole buffer and this is probably
more useful for debugging anyway. Given that we're doing this for
mipi_dsi_dcs_write_seq(), let's also print the buffer for
mipi_dsi_generic_write_seq() in the error case.
It should be noted that the current consensus of DRM folks is that the
mipi_dsi_*_write_seq() should be deprecated due to the non-intuitive
return behavior. A future patch will formally mark them as deprecated
and provide an alternative.
Signed-off-by: Douglas Anderson <[email protected]>
---
Changes in v2:
- Add some comments to the macros about printing and returning.
- Modify commit message now that this is part of a series.
- Change the way err value is handled in prep for next patch.
- Rebased upon patches to avoid theoretical int overflow.
drivers/gpu/drm/drm_mipi_dsi.c | 56 ++++++++++++++++++++++++++++++++++
include/drm/drm_mipi_dsi.h | 41 +++++++++++++------------
2 files changed, 78 insertions(+), 19 deletions(-)
diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index 795001bb7ff1..1e062eda3b88 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -764,6 +764,34 @@ ssize_t mipi_dsi_generic_write(struct mipi_dsi_device *dsi, const void *payload,
}
EXPORT_SYMBOL(mipi_dsi_generic_write);
+/**
+ * mipi_dsi_generic_write_chatty() - mipi_dsi_generic_write() w/ an error log
+ * @dsi: DSI peripheral device
+ * @payload: buffer containing the payload
+ * @size: size of payload buffer
+ *
+ * Like mipi_dsi_generic_write() but includes a dev_err_ratelimited()
+ * call for you and returns 0 upon success, not the number of bytes sent.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int mipi_dsi_generic_write_chatty(struct mipi_dsi_device *dsi,
+ const void *payload, size_t size)
+{
+ struct device *dev = &dsi->dev;
+ ssize_t ret;
+
+ ret = mipi_dsi_generic_write(dsi, payload, size);
+ if (ret < 0) {
+ dev_err_ratelimited(dev, "sending generic data %*ph failed: %d\n",
+ (int)size, payload, (int)ret);
+ return ret;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(mipi_dsi_generic_write_chatty);
+
/**
* mipi_dsi_generic_read() - receive data using a generic read packet
* @dsi: DSI peripheral device
@@ -852,6 +880,34 @@ ssize_t mipi_dsi_dcs_write_buffer(struct mipi_dsi_device *dsi,
}
EXPORT_SYMBOL(mipi_dsi_dcs_write_buffer);
+/**
+ * mipi_dsi_dcs_write_buffer_chatty - mipi_dsi_dcs_write_buffer() w/ an error log
+ * @dsi: DSI peripheral device
+ * @data: buffer containing data to be transmitted
+ * @len: size of transmission buffer
+ *
+ * Like mipi_dsi_dcs_write_buffer() but includes a dev_err_ratelimited()
+ * call for you and returns 0 upon success, not the number of bytes sent.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int mipi_dsi_dcs_write_buffer_chatty(struct mipi_dsi_device *dsi,
+ const void *data, size_t len)
+{
+ struct device *dev = &dsi->dev;
+ ssize_t ret;
+
+ ret = mipi_dsi_dcs_write_buffer(dsi, data, len);
+ if (ret < 0) {
+ dev_err_ratelimited(dev, "sending dcs data %*ph failed: %d\n",
+ (int)len, data, (int)ret);
+ return ret;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(mipi_dsi_dcs_write_buffer_chatty);
+
/**
* mipi_dsi_dcs_write() - send DCS write command
* @dsi: DSI peripheral device
diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 5de2bd62448b..6d68d9927f46 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -256,6 +256,8 @@ int mipi_dsi_picture_parameter_set(struct mipi_dsi_device *dsi,
ssize_t mipi_dsi_generic_write(struct mipi_dsi_device *dsi, const void *payload,
size_t size);
+int mipi_dsi_generic_write_chatty(struct mipi_dsi_device *dsi,
+ const void *payload, size_t size);
ssize_t mipi_dsi_generic_read(struct mipi_dsi_device *dsi, const void *params,
size_t num_params, void *data, size_t size);
@@ -279,6 +281,8 @@ enum mipi_dsi_dcs_tear_mode {
ssize_t mipi_dsi_dcs_write_buffer(struct mipi_dsi_device *dsi,
const void *data, size_t len);
+int mipi_dsi_dcs_write_buffer_chatty(struct mipi_dsi_device *dsi,
+ const void *data, size_t len);
ssize_t mipi_dsi_dcs_write(struct mipi_dsi_device *dsi, u8 cmd,
const void *data, size_t len);
ssize_t mipi_dsi_dcs_read(struct mipi_dsi_device *dsi, u8 cmd, void *data,
@@ -311,40 +315,39 @@ int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
/**
* mipi_dsi_generic_write_seq - transmit data using a generic write packet
+ *
+ * This macro will print errors for you and will RETURN FROM THE CALLING
+ * FUNCTION (yes this is non-intuitive) upon error.
+ *
* @dsi: DSI peripheral device
* @seq: buffer containing the payload
*/
#define mipi_dsi_generic_write_seq(dsi, seq...) \
do { \
static const u8 d[] = { seq }; \
- struct device *dev = &dsi->dev; \
- ssize_t ret; \
- ret = mipi_dsi_generic_write(dsi, d, ARRAY_SIZE(d)); \
- if (ret < 0) { \
- dev_err_ratelimited(dev, "transmit data failed: %d\n", \
- (int)ret); \
+ int ret; \
+ ret = mipi_dsi_generic_write_chatty(dsi, d, ARRAY_SIZE(d)); \
+ if (ret < 0) \
return ret; \
- } \
} while (0)
/**
* mipi_dsi_dcs_write_seq - transmit a DCS command with payload
+ *
+ * This macro will print errors for you and will RETURN FROM THE CALLING
+ * FUNCTION (yes this is non-intuitive) upon error.
+ *
* @dsi: DSI peripheral device
* @cmd: Command
* @seq: buffer containing data to be transmitted
*/
-#define mipi_dsi_dcs_write_seq(dsi, cmd, seq...) \
- do { \
- static const u8 d[] = { cmd, seq }; \
- struct device *dev = &dsi->dev; \
- ssize_t ret; \
- ret = mipi_dsi_dcs_write_buffer(dsi, d, ARRAY_SIZE(d)); \
- if (ret < 0) { \
- dev_err_ratelimited( \
- dev, "sending command %#02x failed: %d\n", \
- cmd, (int)ret); \
- return ret; \
- } \
+#define mipi_dsi_dcs_write_seq(dsi, cmd, seq...) \
+ do { \
+ static const u8 d[] = { cmd, seq }; \
+ int ret; \
+ ret = mipi_dsi_dcs_write_buffer_chatty(dsi, d, ARRAY_SIZE(d)); \
+ if (ret < 0) \
+ return ret; \
} while (0)
/**
--
2.44.0.769.g3c40516874-goog
On Sat, 27 Apr 2024 at 02:59, Douglas Anderson <[email protected]> wrote:
>
> Through a cooperative effort between Hsin-Yi Wang and Dmitry
> Baryshkov, we have realized the dev_err_ratelimited() in the
> mipi_dsi_*_write_seq() macros was causing quite a bit of bloat to the
> kernel. Let's hoist this call into drm_mipi_dsi.c by adding a "chatty"
> version of the functions that includes the print. While doing this,
> add a bit more comments to these macros making it clear that they
> print errors and also that they return out of _the caller's_ function.
>
> Without any changes to clients this gives a dramatic savings. Building
> with my build system shows one example:
>
> $ scripts/bloat-o-meter \
> .../before/panel-novatek-nt36672e.ko \
> .../after/panel-novatek-nt36672e.ko
>
> add/remove: 0/1 grow/shrink: 0/1 up/down: 0/-21496 (-21496)
> Function old new delta
> nt36672e_1080x2408_60hz_init._rs 10320 - -10320
> nt36672e_1080x2408_60hz_init 17412 6236 -11176
> Total: Before=32147, After=10651, chg -66.87%
>
> Note that given the change in location of the print it's harder to
> include the "cmd" in the printout for mipi_dsi_dcs_write_seq() since,
> theoretically, someone could call the new chatty function with a
> zero-size array and it would be illegal to dereference data[0].
> There's a printk format to print the whole buffer and this is probably
> more useful for debugging anyway. Given that we're doing this for
> mipi_dsi_dcs_write_seq(), let's also print the buffer for
> mipi_dsi_generic_write_seq() in the error case.
>
> It should be noted that the current consensus of DRM folks is that the
> mipi_dsi_*_write_seq() should be deprecated due to the non-intuitive
> return behavior. A future patch will formally mark them as deprecated
> and provide an alternative.
>
> Signed-off-by: Douglas Anderson <[email protected]>
> ---
>
> Changes in v2:
> - Add some comments to the macros about printing and returning.
> - Modify commit message now that this is part of a series.
> - Change the way err value is handled in prep for next patch.
> - Rebased upon patches to avoid theoretical int overflow.
>
Reviewed-by: Dmitry Baryshkov <[email protected]>
--
With best wishes
Dmitry